For a little over half an hour, Liverpool’s start to the season had looked like being, if not perfect—it was too open at the back for that—then certainly extremely comfortable. It led newly-promoted Norwich City 3-0 and was playing with increasing fluency. But then, taking a routine goal-kick, the goalkeeper Alisson slipped. He was forced off with what appeared to be a calf strain and, while the precise nature of the problem remains unclear, the fear is that he could miss several weeks of the season. The injury overshadowed a comfortable 4-1 victory.

The only positive for Alisson is that he did not need a stretcher but was able, after treatment and with help, to limp off. That meant an early debut for Adrian, who only completed his free transfer to Liverpool earlier in the week after the previous backup, Simon Mignolet, left the club for Club Brugge. The 32-year-old Spaniard had been a crowd favorite at West Ham before falling behind Lukasz Fabianksi in the pecking order. He did not start a single league game last season and hadn’t played in a competitive fixture since West Ham’s FA Cup fourth-round defeat to AFC Wimbledon in January.

In the context of the game it hardly mattered: the game had long since been won. Adrian had only 20 touches in his 52 minutes on the pitch and was barely involved until pushing a ferocious shot from Moritz Leitner against the post after 63 minutes, and there was little he could do as Teemu Pukki converted Emi Buendia’s through-ball two minutes later. The bigger issue by far from Liverpool’s point of view was the positioning of the full-backs, Andy Robertson playing the Finn onside.

But in the context of Liverpool’s season this could be very significant indeed. Adrian is a fine goalkeeper, although he could hardly be blamed if he were a little rusty, but he does not have Alisson’s ability with his feet. That is vital to how Liverpool play: to operate with a line as high as Jurgen Klopp likes his side to, it’s necessary to have a goalkeeper comfortable operating outside his box, almost as an auxiliary playmaker, sweeping in the space behind the back four. Most immediately, that could impinge on Liverpool in Wednesday’s European Super Cup when Klopp’s side, as Champions League winners, take on the Europa League winners Chelsea in Istanbul.

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Alisson’s injury wasn’t the only concern for Liverpool. In pre-season, Liverpool had looked vulnerable to balls played in behind the full-backs, and that weakness was apparent again as Norwich had seven first-half chances, more than any other away side at Anfield in the past two seasons. Daniel Farke, the Norwich manager, had said that he would not change the approach that took his side to promotion last season but the aggressive style meant his team was left very open.

It took just seven minutes for Grant Hanley to deflect a Divock Origi cross into his own net and a neat Mohamed Salah finish had as good as ended the game as a contest after 19 minutes. Virgil van Dijk headed a third from a corner before an unmarked Origi glanced in a fourth before halftime. A refusal to compromise his principles may be admirable, but there will surely have to be tweaks if there are not to be similarly hefty defeats to Chelsea and Manchester City, both of whom Norwich also face in the next five weeks.

There is a wider issue here too. The last domestic season ended with Manchester City smashing Watford 6-0 in the FA Cup final and it did nothing to dampen concerns about the growing gulf between top and bottom of the league that this season should start in similar fashion. Liverpool, in truth, could have easily have extended its lead in the first 10-15 minutes of the second half before rather switching off, and there were chances at both ends after Pukki’s goal.

It says much for how expectations have changed that a win as comprehensive as this comes niggles and gripes—even before the injury. But it’s that absence of Alisson that looms over this result: an emphatic win but one that perhaps has come with very serious consequences. There will be many at Anfield nervously awaiting the result of his scans.